The aetiology of intellectual disability in Western Australia: a community-based study

Data Linkage: Canadian and Australian Perspectives on a Valuable Methodology for Intellectual and Developmental Disability Research

Data linkage holds great promise for generating new information about people with intellectual and developmental disabilities (IDD) as a population, yet few centers have developed the infrastructure to utilize this methodology. Two examples, from Canada and Australia, describe their efforts in building data linkage capabilities, and how linked databases can be used to identify persons with IDD and used for population-based research. The value of data linkage is illustrated through new estimates of prevalence of IDD; health service utilization patterns; associations with sociodemographic characteristics, and with physical and mental health conditions (e.g., chronic diseases, injury, fertility, and depression); and findings on equity in medical treatments. Examples are provided of findings used for governmental policy and program planning.

Health care utilisation among older persons with intellectual disability and dementia: a registry study

BACKGROUND

Both persons with intellectual disability (ID) and persons with dementia have high disease burdens, and consequently also high health care needs. As life expectancy increases for persons with ID, the group of persons with the dual diagnosis of ID and dementia will become larger.

METHOD

Through national registries, we identified 7936 persons who had received support directed to persons with ID during 2012, and an age- and gender-matched sample from the general population. A national registry was also used to collect information on health care utilisation (excluding primary care) for the period 2002-2012. Health care utilisation was measured as presence and number of planned and unplanned in-patient and out-patient visits, as well as length of stay.

RESULTS

In comparison with persons with ID but without dementia, persons with ID and dementia were more likely to have at least one planned out-patient visit (odds ratio [OR] 8.07), unplanned out-patient visit (OR 2.41), planned in-patient visit (OR 2.76) or unplanned in-patient visit (OR 4.19). However, among those with at least one of each respective outcome, the average number of visits did not differ between those with and without dementia. Persons with ID and dementia were less likely to have at least one planned out-patient visit than persons with dementia in the general population sample (OR 0.40), but more likely to have at least one unplanned in-patient visit (OR 1.90). No statistically significant differences were found for having at least one unplanned out-patient or planned in-patient visit. Nevertheless, among those with at least one unplanned out-patient visit, the number of visits was higher in the general population sample.

CONCLUSIONS

Persons with ID and dementia are less likely to receive planned health care than persons with dementia in the general population. They have, however, higher levels of unplanned health care utilisation. This may be an indication that the current support system is not sufficient to meet the challenges of increased longevity among persons with ID.

Aetiology of severe mental retardation and further genetic analysis by high-resolution microarray in a population-based series of 6- to 17-year-old children

AIM

To investigate the prevalence, co-morbidities and aetiologies of severe mental retardation (SMR) in a cohort of Swedish children and to further penetrate aetiologies in the group with undetermined causes by application of updated clinical-genetic methods.

METHODS

The study was population-based and included children living in the County of Halland in western Sweden in 2004 (born 1987-1998; 46,000 children). Patients were identified through habilitation centres, paediatric clinics and school health services. Patients with unclear prenatal aetiology were investigated with single nucleotide polymorphism (SNP)-array.

RESULTS

Severe mental retardation was identified in 133 children from 132 families, corresponding to a prevalence of 2.9 per 1000 children. There were more males than females (90:43).The aetiology was prenatal in 82 (62%), perinatal in 14 (10%) and postnatal in 8 (6%). In 29 (22 %) children, mainly males with autism, the cause could not be related to the time of birth. In the prenatal group, genetic causes dominated, but still 23 children remained undiagnosed; in 5/19 of these patients, a diagnosis could be made after SNP-array analysis. One or more associated neurological handicaps were found in more than half of the children.

CONCLUSION

Prevalence and co-morbidity were similar to previous Scandinavian studies. High-resolution chromosomal micro-array techniques are valuable diagnostic tools, reducing the number of patients with unexplained SMR.

Prevalence of intellectual disability: a meta-analysis of population-based studies

Intellectual disability is an extremely stigmatizing condition and involves utilization of large public health resources, but most data about its burden is based on studies conducted in developed countries. The aim of this meta-analysis was to collate data from published literature and estimate the prevalence of intellectual disability across all such studies. The review includes studies published between 1980 and 2009, and includes data from populations that provided an overall estimate of the prevalence of intellectual disability. Meta-analysis was done using random effects to account for heterogeneity. Sub-group analyses were also done. The prevalence of intellectual disability across all 52 studies included in the meta-analysis was 10.37/1000 population. The estimates varied according to income group of the country of origin, the age-group of the study population, and study design. The highest rates were seen in countries from low- and middle income countries. Studies based on identification of cases by using psychological assessments or scales showed higher prevalence compared to those using standard diagnostic systems and disability instruments. Prevalence was higher among studies based on children/adolescents, compared to those on adults. Higher prevalence in low and middle income group countries is of concern given the limitations in available resources in such countries to manage intellectual disability. The importance of using standardized diagnostic systems to correctly estimate the burden is underlined. The public health and research implications of this meta-analysis have been discussed.

Estimating the burden of disease attributable to four selected environmental risk factors in South Africa

INTRODUCTION

The first South African National Burden of Disease study quantified the underlying causes of premature mortality and morbidity experienced in South Africa in the year 2000. This was followed by a Comparative Risk Assessment to estimate the contributions of 17 selected risk factors to burden of disease in South Africa. This paper describes the health impact of exposure to four selected environmental risk factors: unsafe water, sanitation and hygiene; indoor air pollution from household use of solid fuels; urban outdoor air pollution and lead exposure.

METHODS

The study followed World Health Organization comparative risk assessment methodology. Population-attributable fractions were calculated and applied to revised burden of disease estimates (deaths and disability adjusted life years, [DALYs]) from the South African Burden of Disease study to obtain the attributable burden for each selected risk factor. The burden attributable to the joint effect of the four environmental risk factors was also estimated taking into account competing risks and common pathways. Monte Carlo simulation-modeling techniques were used to quantify sampling, uncertainty.

RESULTS

Almost 24 000 deaths were attributable to the joint effect of these four environmental risk factors, accounting for 4.6% (95% uncertainty interval 3.8-5.3%) of all deaths in South Africa in 2000. Overall the burden due to these environmental risks was equivalent to 3.7% (95% uncertainty interval 3.4-4.0%) of the total disease burden for South Africa, with unsafe water sanitation and hygiene the main contributor to joint burden. The joint attributable burden was especially high in children under 5 years of age, accounting for 10.8% of total deaths in this age group and 9.7% of burden of disease.

CONCLUSION

This study highlights the public health impact of exposure to environmental risks and the significant burden of preventable disease attributable to exposure to these four major environmental risk factors in South Africa. Evidence-based policies and programs must be developed and implemented to address these risk factors at individual, household, and community levels.

The Croydon Assessment of Learning Study: prevalence and educational identification of mild mental retardation

BACKGROUND

Mild mental retardation is an enduring and impairing condition. Its prevalence has varied widely across different studies from .5 to over 8%, with higher rates in completely ascertained samples. The current study estimates the prevalence of low IQ in the mental retardation range (intellectual disability) in a population sample and examines the factors that relate to educational identification.

METHOD

A total of 2,730 children in school years 8 and 9 attending local authority schools were assessed in school with the group-administered Cognitive Abilities Test (CAT). A sample of 304 pupils at high, moderate and low risk of mild mental retardation was selected for in-depth study. This included the individually measured full-scale IQ (WISC-III(UK)), the Wechsler Quicktest of attainments, the Strengths and Difficulties Questionnaire from parents and teachers and an abbreviated version of the Social Communication Questionnaire.

RESULTS

Of those selected for the in-depth study, 204 (67%) participated, with a greater proportion from the low risk group. A range of prevalence estimates were calculated using different imputation methods and assumptions about individuals not screened. Rates of pupils with WISC IQ < 70 varied from 5.8% to 10.6%. There were no significant gender differences. In contrast to the high prevalence estimates using the WISC, the proportion of pupils scoring in the lowest stanine on the CAT was as expected. Only 15% of those with IQ < 70 had a statement of special educational needs or attended a school for moderate learning difficulties. Behaviour, particularly social communication problems, predicted educational identification.

CONCLUSIONS

The current study produced a high estimate of the prevalence of mild intellectual disability based on the WISC but not on the CAT. The findings highlight that the majority of mild intellectual disability in the UK would not be detected using registers. Cases that are detected by registers are more behaviourally disturbed than others.

Diagnostic investigations in individuals with mental retardation: a systematic literature review of their usefulness

There are no guidelines available for diagnostic studies in patients with mental retardation (MR) established in an evidence-based manner. Here we report such study, based on information from original studies on the results with respect to detected significant anomalies (yield) of six major diagnostic investigations, and evaluate whether the yield differs depending on setting, MR severity, and gender. Results for cytogenetic studies showed the mean yield of chromosome aberrations in classical cytogenetics to be 9.5% (variation: 5.4% in school populations to 13.3% in institute populations; 4.1% in borderline-mild MR to 13.3% in moderate-profound MR; more frequent structural anomalies in females). The median yield of subtelomeric studies was 4.4% (also showing female predominance). For fragile X screening, yields were 5.4% (cytogenetic studies) and 2.0% (molecular studies) (higher yield in moderate-profound MR; checklist use useful). In metabolic investigations, the mean yield of all studies was 1.0% (results depending on neonatal screening programmes; in individual populations higher yield for specific metabolic disorders). Studies on neurological examination all showed a high yield (mean 42.9%; irrespective of setting, degree of MR, and gender). The yield of neuroimaging studies for abnormalities was 30.0% (higher yield if performed on an indicated basis) and the yield for finding a diagnosis based on neuroradiological studies only was 1.3% (no data available on value of negative findings). A very high yield was found for dysmorphologic examination (variation 39-81%). The data from this review allow conclusions for most types of diagnostic investigations in MR patients. Recommendations for further studies are provided.

The outcome of diagnostic studies on the etiology of mental retardation: Considerations on the classification of the causes

In the different studies on the etiology of mental retardation (MR), a diagnosis has been reached in a remarkably variable proportion of cases. This is due to differences in methodology (population examined, age of the patients, degree of MR, time and protocol of investigation, expertise), method of classification (according to timing of defect, type of defect or both), and, in particular the different use of the term diagnosis. The latter varies with the employed criteria (causal vs. pathomorphological vs. pathophysiological), with the degree of exclusiveness (single cause vs. multifactorial/predisposing background factors) and particularly with the degree of implied certainty (definite vs. provisional). All these factors contribute to the fact that in general, the results of different clinical studies on the etiology of MR are not strictly comparable and cannot be pooled. A dynamic method of classification is proposed which combines both time of occurrence and type of defect, and includes the degree of certainty of a diagnosis. The method allows identification of patients which need follow-up and reconsideration of their cases.

Late diagnosis in severe and mild intellectual disability in adulthood

BACKGROUND

The diagnosis of intellectual disability (ID) is highly dependent on a comprehensive personal and family medical history, a complete physical examination and a careful developmental assessment of the patient. Our study intended to: (1) classify the aetiology of mild and severe ID in an adult population of 140 Italian subjects; (2) evaluate the frequency of associated medical conditions; (3) evaluate the age of diagnosis in both groups; and (4) underline the importance of aetiological diagnosis for adult ID patients also.

METHODS

The study involved 140 consecutive adult Italian ID inpatients and outpatients neurologically investigated at the Neurological Institute C. Mondino of Pavia Service for Mental Retardation. A total of 80 patients had mild ID (MID group) (39 females, 41 males), mean age 34 years (range 19-61 years), mean IQ = 64 (range 51-75), and 60 had severe ID (SID group) (32 females, 28 males), mean age 30 years (range 19-69 years). They underwent a complete diagnostic work-up that comprised prenatal, perinatal and postnatal history, physical examinations, laboratory investigations, genetic survey and neuroradiological investigations to determine the aetiology of ID and to evaluate the presence of associated medical conditions.

RESULTS

ID aetiology was classified as prenatal in 34% of the MID and 28% of the SID group. Perinatal and postnatal events were found in 6% of the MID and in 5% of the SID group. Associated medical conditions were found in 97 patients (47% MID and 26% SID). A genetic diagnosis was possible in 6% of patients above 20 years of age and in 5% of patients above 40 years. A diagnosis of cerebral dysgenesis was possible in 5% of patients above 20 years and 4% of patients above 40 years.

CONCLUSIONS

A long interval between the diagnosis of ID and the aetiological definition can be observed in a significant percentage (24%) of our population, leading to unfortunate consequences of late diagnosis: late onset of a specific therapeutic program, genetic counselling that is frequently no more useful, and ineffective prenatal diagnosis, leading to the birth of other affected subjects (for familiar ID).

Genetic syndromes among individuals with mental retardation

Individuals with mental retardation more commonly have malformations and other structural anomalies than individuals without mental retardation. In many cases, the associated anomalies comprise recognizable syndromes caused by genetic or environmental insults. To co-occurrence of structural anomalies with mental retardation thus assists in the diagnostic evaluation, particularly in infants and young children. The coexistence of structural and mental abnormalities also suggests that both originated in the embryonic period of development.

Comparative survival advantage of males with Down syndrome

In virtually all countries life expectancy is longer in females than in males. A multigeneration, population-based dataset was used to investigate whether a gender-specific difference in life expectancy could be determined in a large cohort (n = 1,332) of people with Down syndrome resident in Western Australia. Contrary to the established pattern of longevity in the general population, and in most people with intellectual disability, males with Down syndrome had a significantly greater life expectancy than females with the same disorder. The reasons for this atypical finding are discussed in terms of the patterns of morbidity experienced by people with Down syndrome, especially at early and late stages of their lifespan.

Co-occurrence of developmental disabilities with birth defects

This article begins with a discussion of the concepts of comorbidity and co-occurrence of diseases and health conditions. These concepts are then applied to the literature on the population-based prevalence of developmental disabilities and birth defects. Most of the existing literature focuses on co-occurrence and obtains data from both clinical and administrative sources. Developmental disabilities occur more frequently in children with multiple, rather than with isolated, birth defects. More research, with more sophisticated study designs, will be necessary to further elucidate the contributions of birth defects to the etiology of developmental disabilities, control for other risk factors, and to identify strategies for prevention and intervention services.

The epidemiology of mental retardation: challenges and opportunities in the new millennium

There are a number of problems and challenges in relating the science of epidemiology to mental retardation (MR). These relate to how MR is defined and classified and how these definitions may change over time. These as well as other differences in ascertainment sources and methods need to be considered when comparing MR prevalence over time and place. On the other hand, advances in technology also provide new and efficient methods of data collection both by data linkage and by use of web-based methods to study rare diseases. While prevalence studies have not been individually reviewed, we have examined the range of data including recent studies relating to how prevalence differs according to age, gender, social class and ethnicity. Some problems with available etiological classification systems have been identified. Recent etiological studies, most of which use different classification systems, have been reviewed and explanations have been postulated to account for differences in results. Individual risk factors for MR are considered whilst the option of considering a population as opposed to a high risk strategy to MR prevention is raised. This might well involve improving the social milieu surrounding the occurrence of individual risk factors. The impact of biotechnological advances such as antenatal and neonatal screening and assisted reproduction on MR are discussed. The issue of how inequalities in access to technology may impact on case identification and even have the potential to further widen inequalities is raised. The importance of extending the use of epidemiological tools to study the social, health and economic burden of MR is also emphasized. However, in order to apply to MR the "prevention-intervention-research" cycle, which surely underpins all epidemiology, it is vital to ensure that the methodological challenges we raise are adequately addressed.

Increased risk for developmental disabilities in children who have major birth defects: a population-based study

OBJECTIVE

We sought to quantify the strength of associations between each of four specific developmental disabilities (DDs) and specific types of major birth defects.

METHODS

We linked data from 2 independent surveillance systems, the Metropolitan Atlanta Congenital Defects Program and the Metropolitan Atlanta Developmental Disabilities Surveillance Program. Children with major birth defects (n = 9142; born 1981-1991 in metro Atlanta) and 3- to 10-year-old children who were born between 1981 and 1991 in metro Atlanta and identified between 1991 and 1994 as having mental retardation, cerebral palsy, hearing impairment, or vision impairment (n = 3685) were studied. Prevalence ratio (PR), which is the prevalence of a DD in children with 1 or more major birth defects divided by the prevalence of the same DD in children without major birth defects, was measured.

RESULTS

Among the 9142 children who were born with a major birth defect, 657 (7.2%) had a serious DD compared with 0.9% in children with no major birth defect, yielding a PR of 8.3 (95% confidence interval: 7.6-9.0). In general, the more severe the DD, the higher was the PR. Birth defects that originated in the nervous system and chromosomal defects resulted in the highest PRs for a subsequent DD. For all other categories of birth defects, PRs were lowest when all major birth defects present were confined to a single category (ie, isolated defects). PRs for any DD increased monotonically with the number of coded birth defects per child or the number of different birth defect categories per child, regardless of the severity of the defect or whether defects of the nervous system, chromosomal defects, or "other syndromes" were counted.

CONCLUSIONS

These data highlight the possible early prenatal origins of some DDs and suggest that both the number of coded birth defects present and the number of anatomic systems involved are strongly related to functional outcomes.

Profile of referrals for early childhood developmental delay to ambulatory subspecialty clinics

The objective of this study was to determine the profile and pattern of referral to subspecialty clinics of young children with suspected developmental delay together with the factors prompting their referral. All children under 5 years of age referred to either developmental pediatrics or pediatric neurology clinics at a single tertiary hospital over an 18-month period were prospectively identified. Standardized demographic and referral information were collected at intake, final developmental delay subtype diagnosed was identified, and referring physicians were surveyed regarding factors prompting referral. A total of 224 children met study criteria. There was a marked male preponderance (166/224), especially among those with either cognitive or language delay. Two delay subtypes, global developmental delay and developmental language disorder, accounted for two thirds of the diagnoses made. For slightly more than one third of the children (75/224), the delay subtype diagnosed following specialty evaluation was different from that initially suspected by the referring physician. A mean delay of 15.5 months was observed for the cohort as a whole between initial parental concern and specialty assessment. For referring physicians, the major factor prompting referral was the severity of the observed delay. The most important aspects of the specialty evaluation according to referral sources were the identification of a possible etiology and confirmation of delay. A profile of referrals and the rationale thereof for a cohort of children with suspected developmental delay is presented that, although locale specific, has implications for service provision and training.

Etiologic determination of childhood developmental delay

To determine the etiologic yield in young children with developmental delay referred to sub-specialty clinics for evaluation. Over an 18-month period, all children less than 5 years of age referred to the ambulatory pediatric neurology or developmental pediatrics clinics of the Montreal Children's Hospital for initial evaluation of a suspected developmental delay were enrolled. Features evident on history or physical examination were determined at intake as were the laboratory tests (and their rationale) requested by the evaluating physicians. Six months post initial assessment, detailed chart review was undertaken to determine if an etiology was found and the basis for such a determination. Bivariate and multivariate logistic regression was used to test for associations between factors present at intake and successful ascertainment of an underlying etiology. Two hundred and twenty-four children met study criteria. Etiologic yield varied across childhood developmental delay subtypes, and was 44/80 for global developmental delay [GDD] (55%), 13/22 for motor delay [MD] (59.1%), 3/72 for developmental language disorders [DLD] (4.2%), and 1/50 for autistic spectrum disorders [ASD] (2%). For GDD, the presence of historical features or findings on physical examination was associated with greater likelihood for successful etiologic determination with the following items significant in multiple logistic regression analysis; microcephaly, antenatal toxin exposure, focal findings. For MD, physical findings or the co-existence of a cerebral palsy symptom complex predicted a successful search for etiology. For both groups, the severity of the delay did not predict etiologic yield. For both groups, a small number of etiologic categories accounted for the majority of diagnoses made. Etiologic yield in childhood developmental delay is largely dependent on the specific developmental delay subtype. Paradigms for systematic evaluation of this common child health problem can be suggested, however they await validation.

Etiologic yield of single domain developmental delay: a prospective study

OBJECTIVE

To determine the etiologic yield in young children with single domain developmental delay (either developmental language disorder or isolated motor delay) after a specialty diagnostic evaluation.

METHODS

During an 18-month period, all children <5 years of age, who were consecutively referred to pediatric neurology or developmental pediatric clinics at a single tertiary pediatric center, were prospectively enrolled. Etiologic yield was determined after completion of clinical assessments and selected laboratory studies requested by the evaluating physician.

RESULTS

Seventy-two children (60 boys) were found to have a developmental language disorder, and 22 children (11 boys) had isolated motor delay, of whom 6 had an associated diagnosis of cerebral palsy. An etiologic diagnosis was rarely made in the children with developmental language disorder (3/72, 4.1%). Laboratory investigations (metabolic, cytogenetic, imaging), aside from audiometry, were uniformly uninformative. In those children with isolated motor delay, an etiology was apparent in more than half (13/22, 59%). Slightly more than half (7/13, 54%) of etiologies identified in this group were potentially preventable. Successful etiologic determination in children with motor delay often had an impact on recurrence risk estimation, medical management, or specific therapy offered (8/13, 62%). The presence of physical findings on initial assessment was found to be highly predictive of successful etiologic determination in children with isolated motor delay (13/17 vs 0/5, P =.002).

CONCLUSION

Etiologic yield differs substantially according to the subgroup of single domain developmental delay.

Family data in Rett syndrome: association with other genetic disorders

BACKGROUND

Rett syndrome is a neurological disorder, almost exclusively affecting girls.

METHODOLOGY

Between 1993 and 1995 pedigree data were obtained from families of girls registered with the Australian Rett syndrome database.

RESULTS

Although 21 individual disorders were reported to be present in family members of affected girls, there was no apparent clustering of the same disorder in different families. However it was certain that a geneticist had been involved in only 10.9% of cases.

CONCLUSIONS

Mutations in the MECP2 gene have now been reported in a proportion of sporadic cases. Thus, it will be important to examine this phenotype-genotype correlation in the Australian cohort. Where a mutation is found, prenatal diagnosis in a subsequent pregnancy will be a possibility. Using the Australian population database and in conjunction with the clinical genetic services in each state it is planned to contact families with an affected girl to offer testing and counselling.

Genes on the X chromosome are important in undiagnosed mental retardation

The clinical genetic diagnosis was reviewed in 429 subjects with intellectual disability in the Australian Child and Adolescent Development (ACAD) study of behavioural problems. With minor differences, the overall "general distribution by causation" was similar to that to that found by the Consensus Conference of the American College of Medical Genetics in 1995. There was a significant male excess in the whole series which was shown to reside in those with "autism," those with undiagnosed nonsyndromic mental retardation (NSMR) and those with X-linked monogenic disorders. It is argued that a substantial proportion of undiagnosed NSMR is caused by genes on the X chromosome. Some of the practical problems of assigning individuals to diagnostic groups are discussed.

Etiologic yield of subspecialists' evaluation of young children with global developmental delay

OBJECTIVE

To determine the etiologic yield of subspecialists' evaluation of young children with global developmental delay. In addition, variables that may predict finding an underlying etiology were also identified.

METHODS

All children <5 years of age, referred over an 18-month period to subspecialty services for initial evaluation of a suspected developmental delay, were prospectively enrolled. Diagnostic yield was ascertained after the completion of clinical assessments and laboratory investigations requested by the evaluating physician.

RESULTS

Ninety-nine children (71 boys) were found to have global developmental delay; 96% had a mild or moderate delay documented. An etiologic diagnosis was determined in 44. Four diagnoses (cerebral dysgenesis, hypoxic-ischemic encephalopathy, toxin exposure, chromosomal abnormalities) accounted for 34 of 44 (77%) of the diagnoses made. The presence of co-existing autistic traits was associated with significantly decreased diagnostic yield (0/19 vs 44/80, P <.0001), whereas specific historical features (eg, family history, toxin exposure, and perinatal difficulty; 23/32 vs 21/67, P =.0002) and findings on physical examination (eg, dysmorphology, microcephaly, and focal motor findings; 35/48 vs 9/51, P <.0001) were significantly associated with identifying a diagnosis. Multiple logistic regression analysis identified antenatal toxin exposure, microcephaly, focal motor findings, and the absence of autistic traits as significant predictor variables for the identification of an etiology.

CONCLUSION

An etiologic diagnosis is often possible in the young child with global developmental delay, particularly in the absence of autistic features. Etiologic yield is augmented by presence of specific findings on history or physical examination on initial assessment.

Evaluation of mental retardation: recommendations of a Consensus Conference: American College of Medical Genetics

A Consensus Conference utilizing available literature and expert opinion sponsored by the American College of Medical Genetics in October 1995 evaluated the rational approach to the individual with mental retardation. Although no uniform protocol replaces individual clinician judgement, the consensus recommendations were as follows: 1. The individual with mental retardation, the family, and medical care providers benefit from a focused clinical and laboratory evaluation aimed at establishing causation and in providing counseling, prognosis, recurrence risks, and guidelines for management. 2. Essential elements of the evaluation include a three-generation pedigree: pre-, peri-, and post-natal history, complete physical examination focused on the presence of minor anomalies, neurologic examination, and assessment of the behavioral phenotype. 3. Selective laboratory testing should, in most patients, include a banded karyotype. Fragile X testing should be strongly considered in both males and females with unexplained mental retardation, especially in the presence of a positive family history, a consistent physical and behavioral phenotype and absence of major structural abnormalities. Metabolic testing should be initialed in the presence of suggestive clinical and physical findings. Neuroimaging should be considered in patients without a known diagnosis especially in the presence of neurologic symptoms, cranial contour abnormalities, microcephaly, or macrocephaly. In most situations MRI is the testing modality of choice. 4. Sequential evaluation of the patient, occasionally over several years, is often necessary for diagnosis, allowing for delineation of the physical and behavioral phenotype, a logical approach to ancillary testing and appropriate prognostic and reproductive counseling.

Schizophrenia in people with intellectual disability: the role of pregnancy and birth complications

The literature suggests that mental illness is more common in people with intellectual disability than in the general population. Having reviewed the literature, Turner (1989) [Psychological Medicine 19, 301-14] suggested that about 3% of people with intellectual disability also have schizophrenia. As pregnancy and birth complications (PBCs) occur more commonly in people with intellectual disability than in the general population and are also implicated in the aetiology of schizophrenia, it is possible that these conditions share a common aetiology. This study reports on the occurrence of PBCs in those people with intellectual disability who develop schizophrenia. Fifty people with intellectual disability and schizophrenia were matched for age, sex, degree of intellectual disability and presence of epilepsy with a control group who did not suffer from schizophrenia or a schizophreniform psychosis. The obstetric history was obtained and events rated on a scale specifically designed for this study. This PBCs scale consists of six sub-scales covering areas of general maternal health, pregnancy, delivery, medication in labour, total medication score and neonatal score, as well as an overall total score. The study found that people with intellectual disability who develop schizophrenia have significantly higher rates of PBCs than controls. All of the sub-scales on the PBCs scale were significantly higher in people with schizophrenia, with the exception of the medication scales. Only five out of the 50 people with schizophrenia had not had a major obstetric complication, compared to 13 subjects from the control group. A number of abnormalities were specifically higher in people who later developed schizophrenia. These included: abnormally long or short labour; maternal episiotomy; maternal preeclamptic toxaemia; induction of labour; dysmaturity; maternal smoking in pregnancy; and a delay in neonatal crying. The results suggest that PBCs are important in the aetiology of schizophrenia in people with intellectual disability.

Reported biomedical causes and associated medical conditions for mental retardation among 10-year-old children, metropolitan Atlanta, 1985 to 1987

This report describes biomedical causes of mental retardation (MR) among school-age children and associated medical conditions in children for whom no cause was reported. This study involved 715, 10-year-old children with MR (intelligence quotient [IQ] 70 or less) born between 1975 and 1977. We determined biomedical causes of MR using a hierarchical approach based on the timing of the event (i.e. prenatal, perinatal, or postneonatal). Among children with no identified biomedical cause the occurrence of associated medical conditions was examined. No reported biomedical cause could be found in 78% of children with MR (87% mild, IQ 50 to 70; 57% severe, IQ < 50). Prenatal causes were present in 12%, perinatal causes in 6%, and postneonatal causes in 4%. On the basis of these findings it was concluded that intensive use of public health prevention strategies can reduce the number of children who receive a diagnosis of MR.

Social and biological risk factors for mild and borderline impairment of language comprehension in a cohort of five-year-old children

Biological risk factors during intra-uterine life, delivery and the neonatal period, and measures of social adversity during pregnancy, were studied as predictors of a 'mildly impaired' (50 to 74) or 'borderline' (75 to 84) score on the Peabody Picture Vocabulary Test (PPVT) at aged five years in 3906 children. Biological risk factors in pregnancy were associated with neither PPVT outcome. Gestation of < 36 weeks, > 3 minutes to establishment of respiration and admission to intensive care were associated with a lower PPVT score indicating mild impairment, though only in the unadjusted analyses. A five minute Apgar score of < 5 and male sex were related to borderline scores, though only the latter remained significant after statistical allowance for possible confounding. In contrast, almost all measures of social adversity were related to both PPVT outcomes even after statistical adjustment for the influence of other factors.

Visual impairment in Nordic children. IV. Sex distribution

A Nordic study group of ophthalmologists, NORDSYN, has compiled registers in Denmark, Finland, Iceland and Norway of 2527 visually impaired children aged 0-17 years. This paper is concerned with the sex-distribution in the registers and has documented a statistically significant excess of males in two of the registers (Denmark and Finland). The dominance of males seems to be related to two main conditions: 1. Genetic factors. 2. Perinatal factors. The genetic factors are mainly concerned with X-linked inheritance. The fact that perinatal influences involve visual impairment in males more than in females is difficult to account for. It may be conjectured, that the basis for perinatal visual damage is determined by unknown prenatal, possibly genetic, factors.